Members of the Z zombie monster class are undead creatures often found in graveyards or in the main dungeon. Zombies leave corpses that are already old, so they are unfit for sacrificing, and are likely to be tainted even if eaten immediately. You can tin a zombie's corpse to attempt to gain whatever intrinsic would normally be added by consuming a normal corpse of the same monster type. More dangerously, eating Zombie corpse and then curing the sickness is also possible.
Types of zombies
These monsters are coveted by neutral protection racketeers because they provide a boost to alignment record with only minimal gain in experience. This is helpful to improve the outcome of Prayer without gaining unnecessary levels. This is true for lawful protection racketeers as well, though their options are so common that it's rarely an issue.
Elf zombies leave old elf corpses. These may be tinned and then eaten for the sleep resistance intrinsic, which they have a 67% chance of giving. The high chance comes from the fact that the base level of the elf monster is considerably higher than other base race monsters.
Player first encounter Ettin zombies, well before encountering normal Ettins.
Also, dNethack zombies can now rise from the dead similar to GruntHack zombies. However, they lack the sickness inducing bite. All non-undead will attack zombies on sight. Any monster killed by a zombie will eventually revive as one if a corpse is left, however the player will not (as of yet).
Even in death, the half-dragon zombie retains the half-dragon breath attack it had in life.
The zombie is a mindless animated corpse. It originates from Haitian folklore. The etymology comes from African or Caribbean creole of related concepts.
The folklore of the Ghoul is a bit unclear, but it is not considered a Zombie.
The zombi... is a soulless human corpse, still dead, but
taken from the grave and endowed by sorcery with a
mechanical semblance of life, -- it is a dead body which is
made to walk and act and move as if it were alive.
[ W. B. Seabrook ]